Reverse circulation underreamer



April 14, A1970 c. H. LEATHERS ETAL 3,506,071

REVERSE CIRCULATION NDERREAMER 3 Sheets-Sheet 1 Filed Aug. 20, 1968 April 14, 1970 C. H. LEATHERs ETAI- REVERSE CIRCULATION UNDERREAMER April 14, 1970 H -LEATHERS E'AL 3,506,077l

v REVERSE CIRCULATION UNDERREAMER I Filed Aug. 2o. 196e 5 Sheets-Sheet 3 Mvg/vroeg. Wees/f. JZ. aucfzn ZHRE/vcFJLEm/IER r A I i f n United States Patent O 3,506,077 REVERSE CIRCULATION UNDERREAMER Clarence H. Leathers, Redondo Beach, and Virgil R.

Douglas, Huntington Park, Calif., assignors to Grant Oil Tool Company, Los Angeles, Calif., a corporation of California Filed Aug. 20, 1968, Ser. No. 754,022 Int. Cl. E21b 9/26 U.S. Cl. 175--267 5 Claims ABSTRACT F THE DISCLOSURE The present invention is a well bore underreamer capable of being opened by forward or reverse circulation of drilling fluid'in the bore. Means are provided in the construction of the underreamer to utilize a fluid pressure differential through the tool in either the reverse or forward direction to open the blades of the tool.

BACKGROUND OF THE INVENTION In the present state of the art expanding hole openers or underreamers which open to their full diameter downhole to expand the diameter of a well bore below a predetermined depth are well known. Underreamers known to the art, however, are such that the blades or cutters can be opened only by the flow of fluid in the direction of forward circulation. In forward circulation the drilling fluid passes downwardly through the drill string and upwardly in the well bore annulus surrounding the drill string. In reverse circulation the drilling fluid is moved downwardly in the annulus and upwardly through the drill string bore. It is the upward passage of the drilling fluid which carries the debris and cuttings from the hole. In conventional down-hole blade opening devices the opening of the blades is achieved by reason of the descending column of iluid in the drill string which is not possible for opening down-hole tools when reverse circulation is employed. Reverse circulation is advantageous in many drilling operations since the'upward velocity through the drill string bore is much greater than that which occurs by the passage of fluid upwardly in the annulus. It can be seen that in reverse circulation it is necessary to have a substantially unrestricted passage through the drill stringA for the passage of the cuttings.

SUMMARY OF THE INVENTION The present invention is an underreamer construction in which underreaming blades are movable to a cutting position by longitudinal movement of a plunger assembly within the bore of the underreamer. The plunger assembly is so constructed and arranged in combination with the underreamer tool body'that the plunger assembly is moved, to in turn move the cutting blades to an open position, by the circulation of drilling fluid through the tool body in either a forward or reverse circulation direction.

Accordingly, it is a primary object of the present invention to provide a well bore underreamer which can be opened to its full reaming diameter by uid in the drill string during both reverse and forward circulation.

It is another object of the present invention to provide an underreamer construction by which the cutters are opened by upward flow of lluid through the bore of the drill string without undue restriction of the bore to allow free passage of fluid carrying cuttings and debris through the bore of the underreamer.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof will be better understood from the ice following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention.

DESCRIPTION OF THE DRAWINGS FIGURE 1 is a view of the underreamer of the present invention shown partially schematically in elevation in the bore of a well being drilled;

FIGURES 2a, 2b and 2c are views in sectional elevation showing the presently preferred embodiment of the invention in the running in condition with the underreaming blades in the closed condition;

FIGURES 3a and 3b are views similar to FIGURES 2a, 2b and 2c of the presently preferred embodiment of the present invention in the forward circulation condition, i.e., with the blades open in response to forward circulation of drilling fluid;

FIGURES 4a and 4b are views in sectional elevation similar to FIGURES 2a, 2b, 2c and 3a and 3b b-ut in the reverse circulation condition, i.e., with the blades open in response to reverse circulation of drilling fluid;

FIGURE 5 is a sectional view taken along line 5 5 of FIGURE 2; and

FIGURE 6l is a sectional view taken along line 6 6 of FIGURE 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, a presently preferred embodiment of the present invention is shown in FIG- URE 2 in the closed position of the underreaming blades. In FIGURE 3 the blades are shown in open position in the forward circulation configuration and in FIGURE 4 in the open position and reverse circulation configuration. Referring now particularly to FIGURES 1 and 2, the underreamer of the present invention includes an elongate tubular body 10 adapted to be connected to the lower end of a drill string 11 by a conventional pin 12 or box end at the upper end of the body 10i. For manufacturing purposes and assembly of component parts within the body 10 the body is formed of a lower 14, intermediate 15 and upper 16 section. The sections are threadably connected to form the body 10 which will be considered as an integral body for purposes of discussion. Thus, the body 10 is an elongate tubular body having an upper pin end 12 and a bull nose 17 at the lower end in this embodiment. A flow passage 20' is dened through the body and is of various diameters along the length of the tool as described more fully hereinafter.

lWhen the tool is being used in forward circulation operation the drilling iluid passes downwardly through the interior of the drill string, through the iiow passage of the tool and upwardly in the bore hole through the annulus surrounding the drill string. In reverse circulation the circulating fluid flows downwardly through the annulus and upwardly through the ow passage 20.

A plurality of blade pockets 21 are defined through the body wall near the lower end of the tool body for the accommodation of the underreamer blades. The blade pockets or openings 21, are circumferentially spaced about the tool body. One such blade, 22 and pocket 21 are shown in FIGURES 2-4. The underreamer blade is pivotally mounted on a pivot pin 23 extended on a chord through the body wall and pocket such that the blade 22 is pivotable from a closed position Within the confines of the tool body, as shown in FIGURE 2 to an open position at which it is pivoted radially outwardly to the open, or cutting position, as shown in FIGURES 3 and 4.

The inner end of the blade, i.e., the blade. section extending radially inwardly of the pivot pin 23, has gear teeth 26 which protrude inwardly beyond the interior wall of the body and into engagement with a plunger 25. The gear tooth and rack engagement of the blade and plunger is such that longitudinal movement of the plunger causes the blade to be pivoted. Thus, movement of the plunger downwardly causes the blade to be pivoted outwardly from the closed to the open position and upward Imovement of the plunger causes the blade to be moved to the closed position. The plunger is an elongate tubular member having a flow passage 26a therethrough and extends from a lower end 28 which includes a rack section in engagement with the gear teeth 26 of the underreamer blade to an upper end 29. The upper end of the plunger is a piston head 30 having an upper piston face 31 and a lower piston face 32. As can be seen with reference to FIGURE 2 the plunger is of varying inside and outside diameters. The maximum outside diameter occurs at the piston head while the minimum outside diameter occurs at the lower end of the plunger. The piston head is of substantially greater diameter than the lower portions of the plunger body and thereby defines a shoulder which has been termed the lower piston face 32. The piston head is provided with a piston ring 33 which is in sealing engagement with the interior wall of the tool body. The tool body throughout that portion of the length immediately above and below the piston head 30 is of an inside diameter substantially equal to the outside diameter of the piston head. The decreased diameter of the plunger below the lower piston face 32 thereby denes a lower annular chamber 35 between the interior wail of the tool body. The chamber 35 then terminates in a shoulder 36 the lower end of the chamber at which the inside diameter of the tool body is decreased to the outside diameter of the plunger at this longitudinal position. The chamber 35 is sealed at one end by a seal 37 and at the other end by the piston ring 33.- A spring 38 in compression is mounted between the lower piston face 32 and the body shoulder 36 to thereby urge the plunger 25 upwardly' and thus, the blade to the closed position. The uppermost limit of travel is that position shown in FIGURE 2 at which position the plunger is limited by the engagement of the plunger with the gear teeth on the blade.

Positioned above the plunger 25 is an upper plunger assembly 40 which is again longitudinally movable within the tool body. The upper plunger assembly 40` is an elongate tubular member which includes in general terms, an elongate portion 40a having a lower end collar 40b of increased diameter and an upper piston assembly 40C of increased diameter. The intermediate portion 40b of the upper plunger assembly has a uniform outside diameter from the lower collar section 40b to the lower face of the upper piston assembly 40e which lower face is y designated as 42. To accommodate the lower end collar assembly and the upper piston the tool body denes an intermediate annular chamber 44 surrounding a lower portion of the lower length of the plunger assembly and an upper annular chamber 45 to accommodate the upper piston assembly. The intermediate annular chamber 44 -is coextensive with the lower chamber 35 and is divided from the lower chamber only by the piston head 33 and the end collar assembly 40b of the upper plunger. The upper end of the annular chamber 44 is therefore dened by the shoulder 43 and the lower end collar assembly of the upper plunger. A lirnit collar 47 is provided about the upper plunger assembly and is in abutting relation with the interior shoulder 43 formed in the tool body to limit the upward travel to the upper plunger to the position substantially shown in FIGURE 2. At this position the lower end of the upper plunger assembly is spaced rrom the upper end of the plunger 25 to provide a radial passage 50 for the ow of circulating tluid outwardly from the ow passage through the tool body to thereby expose the piston face 31 of the plunger and the lower transverse surface of the collar assembly of the upper plunger to the pressure of the fluid at the longitudinal position of the radial passage 50. Thus, in FIGURE 2 both the plunger 25 and the upper plunger 40 are shown in their uppermost position. The lower end collar of the upper plunger assembly includes a collar 51KV to which is atlixed a sealing ring 53 with the sealing ring having an outside diameter in sliding sealing contact with the interior wall of the tool body such that a lower transverse face 55 is provided on the upper plunger assembly. A spring holder 58 is positioned about the plunger sleeve and is stationary with respect to the tool body to thereby define the lower end of the intermediate annular chamber 44. A spring 59 is positioned between the spring holder and the limit coliar 47 in order to urge the plunger assembly 40 upwardly to the position shown in FIGURE 2. The end collar assembly is then movable in sliding sealing engagement with the wall of the tool body below the spring holder 58.

The upper piston at the upper end of the plunger assembly includes a piston body 60 and a piston ring 61 adapted to form a fluid sealing sliding engagement with the interior wall of the tool body throughout the longitudinal portion thereof which forms the upper annular chamber 45. The upper annular chamber is thus adapted to act as a cylinder for the upward and downward movement of the upper piston. The outer diameter of the sleeve portion of the upper assembly (i.e., that elongate upper plunger portion designated as 40a), has a diameter which is less than the inside diameter of the tool body throughout that portion of the length of the tool body. An annular passageway 70 is thereby provided between the lower end of the annular chamber 45 and the intermediate chamber 44. This allows for the equalization of fluid pressure between the chambers 44 and 45. A by-pass passageway 71 is then provided through the wall of the tool body between the intermediate annular chamber 44 and the lower annular chamber 35. The location of the by-pass 71 is such that regardless of the position of the piston of the plunger assembly 25 and the lower end of the upper plunger assembly 40, the by-pass passageway assures the equalization of fluid pressure between the intermediate and lower annular chambers. This is provided by having a radial 72 opening to the longitudinally extending passageway such radial opening 72 being above the spring holder and a second radial opening 73 being below the limit of travel of the piston 33.

There is also provided a series of radial openings 74 through the sleeve of the upper plunger assembly in communication with the upper annular chamber 45 such that fluid pressure within the flow passage through the upper plunger assembly in that longitudinal position corresponding to the upper annular chamber 45 is communicated t0 the upper annular chamber. Such pressure is thus equalized through the annular passageway 70 into the intermediate chamber 44 through the by-pass passageway 71 and into the lower annular oamber 35. Accordingly, it can be seen that the uid pressure within the three annular chambers described is equal to the pressure of the circulating fluid at that location within the upper plunger assembly which coincides with the annular chamber 45 beneath the upper piston head. Means are then provided in the underreamer of the present invention for varying the pressure or" the circulating fluid above and below the longitudinal location of the upper annular chamber 45 dependent upon whether the circulation of the tluid is in the reverse or the forward direction. In the presently preferred embodiment a series of longitudinally spaced apart annular plates 75 are inserted in the flow passage through the upper plunger assembly 40 between the lower end thereof and the radial passages 74 in communication with the upper annular chamber. In the embodiment shown 14 such annular restrictions are employed. The use of a large plurality of such annular restrictions creates a large pressure differen- 7 8 an annular passageway delined by said body between face during upward movement of liquid through said said upper and intermediate chambers for equalizing plunger is a spaced apart series of transverse annular the fluid pressure therein; plates positioned in said plunger assembly in said upper a by-pass passageway dened through the wall of said annular chamber.

body between said lower and intermediate chambers 5 5. The apparatus as dened in claim 4 in which said to equalize fluid pressure in said lower and intervalve means is a flapper valve at the upper face of said mediate chambers; upper piston. check valve means for allowing passage of liquid only References Cited upwardly thfollgh Said upper Piston? s UNITED STATES PATENTS means for reducing the pressure 1n sald upper annular lo chamber during upward progress of liquid through 211771721 10/1939 Johnson 175-267X said plunger to create a pressure differential across v 212771989 3/1942 Kmnear 175-267X said lower piston to urge said plunger downwardly; 214571628 12/1948 Baker 175*267 X said upper plunger assembly being movable downwardly 217551070 7/1956 Kammerer 175-267 in response to downward fluid circulation to in turn 15 218091016 10/1957 Kammerer 175-267 move said plunger downwardly; and 218471189 8/1958 Shook 175--267 said blades being moved to the open position by co- 311961961 7/1965 Kammerer 175-267 action with said plunger during the downward move- 312831834 11/1966 Kammerer UST-267 ment thereof. 4. The apparatus as defined in claim 3 in which the 20 NILE C. BYERS, JR., Primary Examiner means for lowering the pressure below said second piston tial between the radial openings 74 and the lower end of the upper plunger assembly by the passage of the circulating fluid through such restrictions without necessitating such a small restriction that blockage is occasioned -by reason of cuttings and other materials flowing therethrough. It has been found that by utilizing ten such restrictive orifices four times the resistance to fluid flow is accomplished as by using one such restriction. The need for creating a substantial fluid pressure differential for operation of the device but without undue restruction of the flow passage through the tool is necessary in reverse circulation where cuttings are being carried upwardly through the tool and thus through the flow passage. In forward circulation, cuttings are being moved upwardly through the annulus surrounding the tool and only relatively clean circulating fluid passes downwardly through the flow passageway. The requirement against undue restriction is therefore not essential. In the presently preferred embodiment the means for creating a pressure differential above and below the annular chamber 45 in forward circulation is obtained by means of a fiapper valve 76 pivotally mounted on the plunger assembly above the upper piston. Thus, as shown particularly in FIGURE 2 an elongate sleeve 77 is attached to the upper plunger assembly above the upper piston face and a flapper valve is positioned within the sleeve pivotable about a pivot pin 78. The apper valve is pivotable upwardly in order to permit the full opening of the flow passage when the fluid flow is in the upward or reverse circulation direction. Conversely, an annular seat is provided for the flapper valve so that when it is moved to its Seated position 'by reason of downward flow of circulating fluid through the tool the flapper valve is retained in the closed position such that an orifice 79 through the center of the valve allows restricted passage downwardly through the tool. Thus, with the valve closed a substantial pressure differential is built up between the fluid above the upper piston and the fluid below the flapper valve. Accordingly, with the llapper valve closed and fluid flowing downwardly the pressure within the annular chamber 45 is less than that above the flapper valve and upon the piston face.

Further explanation of the utilization of the pressure differential of flowing fluid through the tool in both the forward and reverse circulation direction in order to open the underreamer on the commencement of such circulation can be best seen by reference to the operation of the tool in both configurations. Thus, referring to FIGURES 2. and 3, in FIGURE 2 the device is shown in the runningin condition which it will assume by reason of the forces of the springs and with no fluid flowing. When used for reverse circulation, upon commencement of circulation the circulating fluid flows downwardly through the annulus, upwardly through the bull nose and into the fluid passage 20 through the tool. As it progresses upwardly and reaches the series of annular restrictions a pressure differential is created with a higher pressure at the lower end of the upper plunger assembly and thus upon the piston face than at the area of the upper plunger assembly which is in communication with the upper annular chamber 45. That is, the fluid pressure at the radial passage 50 is substantially greater than the fluid pressure at the radial passages 74 to the upper annular chamber 45. The lower pressure within the annular chamber 45 is transmitted to the intermediate chamber through the annulus 70 thence through the by-pass 71 and into the lower chamber 35. There then exists a substantial pressure differential between the upper piston face and the lower piston face to the lower plunger. There also exists an` upward force against the lower collar assembly of the upper plunger which retains the upper plunger assembly in its upward position. The force differential across the piston of the lower plunger causes the plunger to be moved downwardly against the force of the spring and such downward movement causes the underreamer blade to be opened as described hereinbefore.

Referring now to FIGURES 2 and 4, in the forward circulation utilization of the underreamer of the present invention the circulating fluid upon commencement of flow is moving downwardly through the flow passage and upwardly in the annulus surrounding the tool. Downward flow of the circulating fluid causes the flapper valve to be closed and to be retained in the closed position. The orifice through the flapper valve causes the pressure differential to exist wherein high pressure exists upwardly of the flapper valve and the lower .pressure exists downwardly therefrom. The lower pressure is transmitted through the radial opening into the upper annular chamber through the passage and into the intermediate chamber, thence through the by-pass and into the lower annular chamber. With a lesser pressure on the lower face of the upper and lower piston the upper piston causes the upper plunger assembly to be moved downwardly until the lower end thereof strikes the upper end of the plunger 25 to in turn cause it to move downwardly and open the underreamer blades as described hereinbefore.

Although a particular arrangement of the invention has been illustrated above by, way of example, it is not intended that the invention be limited thereto. Accordingly, the invention should be considered to include any and all modifications, alterations or equivalent arrangements falling within the scope of the annexed claims.

Having thus described the invention, what is claimed is:

1. A well bore underreamer comprising:

an elongate tubular body;

a plurality of cutter blades pivotally mounted upon said body, said blades being pivotable from a first closed position to a second open position;

a plunger longitudinally movable within said body, said plunger being in coacting engagement with said blades to move said blades from said first to said second position in response to longitudinal movement of said plunger;

said plunger including a piston having first and second piston faces, said first face facing upwardly in the well orientation of said tool;

said plunger being movable downward in response to fluid pressure on said first face;

means for by-passing fluid pressure within said tool when fluid is flowing upwardly through said tool whereby a lesser pressure is maintained on said second face of said piston during both the upward and downward flow of fluid through said tool body.

2. The apparatus as defined in claim 1 including bypass passage within the wall of said tool for communication of fluid to equalize the fluid pressure above and below said piston faces.

3. A well bore underreamer comprising:

an elongate tubular body adapted to be connected into a drill string;

a plurality of cutter blades pivotally mounted upon said body, said blades being pivotable from a first closed position to a second open position;

' a plunger longitudinally movably disposed in said body,

said plunger being an elongate tubular member having a flow passage therethrough;

a lower piston head at the upper end of said plunger, said piston head having an upwardly facing first face and a downwardly facing annular second face of lesser area than said first face;

said tool body defining a lower annular chamber below said second piston face;

an upper plunger assembly positioned above said plunger, said plunger assembly being an elongate tubular member longitudinally movable within said tool body and having an upper piston at the upper end thereof;

said tool body defining an intermediate annular chamber surrounding a lower portion of said upper plunger assembly and an upper annular chamber below said upper piston face, said upper piston being longitudinally movable within said upper chamber; 

